Can a shingles rash start flat and itchy before blisters develop? i had ch px as a child. just developed a rash on the right side of my chest

Yes.: Yes, in fact that's the most common way it starts. Shingles is almost always on only one side of the body, often in a "stripe" like pattern. The lesion go from flat reddish, to clear blisters, to cloudy blisters, to open blisters, to crusted lesions. Early treatment with a type of antiviral drug can reduce the risk of chronic pain afterward (post-herpetic neuralgia). See doctor soon.

Shingles: It is possible to have the rash change over time, but a more common presentation is for there to be pain in the area where the future rash will develop. This pain, rather than itching, leads into the full blown condition.